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ALD cycle count and deposition time calculator

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KEY POINTS

ALD builds films 0.3 to 2 Å per cycle, so the number of cycles = target thickness ÷ GPC sets thickness precisely. Three nm of HfO₂ (GPC about 1 Å) takes about 30 cycles. Most of the cycle is purge, and at a few nm per minute or less deposition is slow, but ALD coats the inside of deep trenches uniformly.

Inputs

Film (typical conditions)Growth per cycle GPC (Å/cycle)Target thickness (nm)Nucleation delay (cycles with no growth) (cycles)Precursor pulse (s)Purge 1 (s)Reactant pulse (oxidant, nitrogen source or plasma) (s)Purge 2 (s)Wafers per run (1 for single-wafer) (wafers)Overhead per run (transfer, heat-up, pump-down) (min)

Required cycles35cycles

Time per cycle4.70s

Deposition time2.74 min

Throughput12.7wafers/h

Effective deposition rate1.277nm/min

Purge share of cycle time85%

More than 70% of the cycle is purge. Shortening purge time, for example with spatial ALD or a smaller chamber volume, is the biggest opportunity to raise throughput.

GPC varies with temperature (the ALD window), precursor and substrate. The table values are typical literature values; replace them with measurements on your tool. Nucleation delay at the start of deposition differs greatly by substrate (Si, SiO₂, metal).

Films compared (target 3 nm, single-wafer)

Film	GPC	Cycles	Deposition time	Effective deposition rate
Al₂O₃ (TMA / H₂O)	1.1 Å	28	1.0 min	3.00 nm/min
HfO₂ (TEMAHf / H₂O)	1 Å	30	2.4 min	1.28 nm/min
ZrO₂ (TEMAZr / O₃)	0.9 Å	34	2.8 min	1.08 nm/min
SiO₂ (aminosilane / O₂ plasma, PEALD)	1.2 Å	25	1.4 min	2.18 nm/min
SiN (DCS / NH₃ plasma, PEALD)	0.4 Å	75	11.9 min	0.25 nm/min
TiN (TiCl₄ / NH₃, thermal ALD)	0.4 Å	75	4.5 min	0.67 nm/min
ZnO (DEZ / H₂O)	1.9 Å	16	0.6 min	5.18 nm/min

Why ALD is used despite being slow

ALD (atomic layer deposition) supplies a precursor and a reactant alternately and relies on self-limiting reactions, where only what can adsorb on the surface reacts, to build the film less than one atomic layer (0.3 to 2 Å) per cycle. At a few nm per minute or less it is orders of magnitude slower than CVD, but the number of cycles sets thickness precisely and the film coats the inside of deep holes and trenches uniformly.

ALD is indispensable where films are a few nm thick and uniformity comes first: high-k gate dielectrics, DRAM capacitor dielectrics, the deep memory holes of 3D NAND and spacers for self-aligned double patterning. To raise productivity, fabs use batch furnaces that process many wafers at once and spatial ALD tools that rotate wafers through separate precursor zones.

FAQ

What is growth per cycle (GPC)?

The film thickness added by one complete ALD cycle, typically 0.3 to 2 Å. It depends on precursor, temperature and substrate.

How can ALD throughput be raised?

Shorten purges with smaller chambers, process many wafers at once in batch furnaces, or use spatial ALD, which moves wafers through separate precursor zones instead of pulsing gases.

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Last updated: October 23, 2026